1. Field of the invention
This invention relates to water-based concrete parting agents containing selected oils and emulsifiers, to a process for their production and to the use of the mixtures of selected oils and emulsifiers for the production of water-based concrete parting agents.
2. Discussion of Related Art
Parting agents for concrete formwork and forms are known, for example, from the corresponding guideline of the "Concrete Technology" Committee of the Deutscher Beton-Verein e.V., Wiesbaden (1980) and from H. Reul, Handbuch Bauchemie, Verlag fur Chem. Industrie, Ziolkowsky AG, Augsburg, 1991, pages 319 et seq. They are applied to the formwork before the fresh concrete is placed therein and are intended to reduce adhesion between concrete and formwork during stripping and to avoid damage to the concrete surface and to the formwork. This is supposed to increase the number of times the formwork material can be used.
The parting agents generally contain an oil component and various additives, for example rustproofing agents, antioxidants, anti-pore agents, preservatives, wetting agents, coupling agents and emulsifiers. The oil component may be selected from various classes of oils and mixtures thereof, for example mineral oils or white oils, waxes; triglycerides based on vegetable or animal oils or fats or fat derivatives. It is of particular advantage to use the concrete parting agents in the form of an aqueous emulsion. If they are to be used in this form, the parting agents generally contain emulsifiers, such as soaps, ethoxylated fatty acids and ethoxylated alkylphenols or petroleum sulfonates in quantities of about 10 to 30% by weight, based on the oil component. Normally, the parting agents are not delivered to the point of use in the form of an emulsion, but rather in the form of a concentrate which is diluted immediately before use.
The parting agents used today have various disadvantages. Mineral oils or white oils as the oil component are not sufficiently biodegradable. Although triglycerides based on native oils, for example rapeseed oil, are readily biodegradable, they have relatively high viscosities unfavorable for use. In addition, saponification of the oil by alkaline constituents of the concrete can result in the precipitation of calcium soaps, a phenomenon known as "sanding up", which can cause adhesion problems during further processing of the concrete. Fatty acid esters show similar behavior. It has already been proposed to remedy the situation by using distillation residues from the production of fatty alcohols, but unfortunately it has been found that these compounds can only be partly used as the oil component, as described for example in DD-A5 290 439. In this case, the oil component used consists of 80 to 90% by weight of mineral oil with an addition of 4 to 10% by weight of a mixture of saturated and unsaturated wax esters containing 32 to 36 carbon atoms, saturated and unsaturated fatty alcohols containing 24 to 32 carbon atoms and hydrocarbon. In addition, the wax esters present in the mixture can saponify which gives rise to the adhesion problems described above. WO 95/18704 (Henkel) describes concrete parting agents which contain optionally unsaturated fatty alcohols or Guerbet alcohols as oil components and nonionic surfactants in the form of alkylene oxide adducts with suitable H-acid compounds as emulsifiers. European patent application EP-A 0 561 465 discloses mold release agents which contain esters of sterically hindered polyhydric alcohols as compulsory components. The use of monohydric alcohols is described as a way of reducing the emulsifier content. British patent application GB-A 1,294,038 describes a process for the production of concrete parting agents in which monohydric alcohols are used in combination with cationic surfactants.
The emulsifiers used for the production of aqueous emulsions are also not without their problems from the applicational point of view. To produce emulsions, it has hitherto been necessary to use relatively large quantities of emulsifier which, unfortunately, has an adverse effect on the rainproof behavior of the parting agents. In addition, if the emulsifier content is high, re-emulsification can occur at the interface with the alkaline cement, some of the parting agent penetrating into the surface of the concrete. These residues of parting agent can subsequently lead to the above-mentioned problems affecting the adhesion of paints or plasters.
Accordingly, there is a significant demand for concrete parting agents which are readily biodegradable and which have none of the disadvantages of known compounds, such as high viscosity, surface deficiencies or sanding up. Another disadvantage is that, hitherto, known concrete parting agents could at best be assigned to Water Hazard Class 1. The requirements which an environmentally compatible concrete parting agent should satisfy are explained by way of example in RAL UZ 64 "Biologisch schnell abbaubare Schmierstoffe und Schalole" of June, 1991.
Accordingly, the problem addressed by the present invention was to provide concrete parting agents having improved ecological compatibility which would be distinguished by high resistance to saponification and which would form stable liquid emulsions, even at low temperatures. In addition, the viscosity of the emulsions would be so low that they could be sprayed without difficulty. Finally, the concrete parting agents according to the invention would uniformly wet various formwork materials and would adhere firmly to them.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about".